Collision avoidance system

This article is about collision avoidance in automobiles. For other uses, see
Collision avoidance.

A collision avoidance system, also known as a precrash system, forward collision warning system, or collision mitigating system, is an automobile safety system designed to prevent or reduce the severity of a collision. It uses radar (all-weather) and sometimes laser (LIDAR) and camera (employing image recognition) to detect an imminent crash. GPS sensors can detect fixed dangers such as approaching stop signs through a location database.[1][2][3]

Once an impending collision is detected, these systems provide a warning to the driver. When the collision becomes imminent, they take action autonomously without any driver input (by braking or steering or both). Collision avoidance by braking is appropriate at low vehicle speeds (e.g. below 50 km/h (31 mph)), while collision avoidance by steering may be more appropriate at higher vehicle speeds if lanes are clear.[4] Cars with collision avoidance may also be equipped with adaptive cruise control, using the same forward-looking sensors.

In March 2016, the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety announced the manufacturers of 99% of U.S. automobiles had agreed to include automatic emergency braking systems as standard on virtually all new cars sold in the U.S. by 2022.[5] In Europe, there was a related agreement about advanced emergency braking system (AEBS) or autonomous emergency braking (AEB) in 2012.[6]United Nations Economic Commission for Europe (UNECE) has announced that this kind of system will become mandatory for new heavy vehicles starting in 2015.[7] NHTSA projected that the ensuing accelerated rollout of automatic emergency braking would prevent an estimated 28,000 collisions and 12,000 injuries.[5] In India, Autonomous Emergency Braking system (AEB) could become mandatory on new cars by 2022.[8].[9].

AEB differs from Forward Collision Warning: FCW alert the driver with a warning but does not by itself brake the vehicle.[10]

Autonomous: the system acts independently of the driver to avoid or mitigate the accident.

Emergency: the system will intervene only in a critical situation.

Braking: the system tries to avoid the accident by applying the brakes.

History

Early warning systems were attempted as early as the late 1950s. An example is Cadillac, which developed a prototype vehicle named the Cadillac Cyclone which used the new radar technology to detect objects in front of the car with the radar sensors mounted inside "nose cones". It was deemed too costly to manufacture.

The first modern forward collision avoidance system was demonstrated in 1995 by a team of scientists and engineers at Hughes Research Laboratories in Malibu, California. The project was funded by Delco Electronics, and was led by HRL physicist Ross D. Olney. The technology was marketed as Forewarn. The system was radar based - a technology that was readily available at Hughes Electronics, but not commercially elsewhere. A small custom fabricated radar antenna was developed specifically for this automotive application at 77 GHz.[12] In August 1997, the first production laser adaptive cruise control on a Toyota vehicle was introduced on the Celsior model (Japan only).

Between 2010 and 2014, Euro-ncap rewarded various constructors whose system had AEB features.

EuroNCAP rewards

Maker

Year

System

BMW

2014

BMW Pedestrian Warning with City Brake Activation

FIAT

2013

FIAT City Brake Control

Mitsubishi

2013

Mitsubishi Forward Collision Mitigation

Skoda

2013

Skoda Front Assistant

Audi

2012

Audi Pre Sense Front

Audi

2012

Audi Pre Sense Front Plus

VW

2012

Volkswagen Front Assist

Ford

2011

Ford Active City Stop

Ford

2011

Ford Forward Alert

Mercedes-Benz

2011

Mercedes-Benz Collision Prevention Assist

VW

2011

Volkswagen City Emergency Brake

Honda

2010

Honda Collision Mitigation Brake System

Mercedes-Benz

2010

Mercedes-Benz PRE-SAFE® Brake

Volvo

2010

Volvo City Safety

In the early-2000s, the U.S. National Highway Traffic Safety Administration (NHTSA) studied whether to make frontal collision warning systems and lane departure warning systems mandatory.[14] In 2011, the European Commission investigated the stimulation of "collision mitigation by braking" systems.[15] Mandatory fitting (extra cost option) of Advanced Emergency Braking Systems in commercial vehicles was scheduled to be implemented on 1 November 2013 for new vehicle types and on 1 November 2015 for all new vehicles in the European Union.[16] According to the "impact assessment",[17] this could prevent around 5,000 fatalities and 50,000 serious injuries per year across the EU.

AEB in Australia

Benefits

A 2012 study[19] by the Insurance Institute for Highway Safety examined how particular features of crash-avoidance systems affected the number of claims under various forms of insurance coverage. The findings indicate that two crash-avoidance features provide the biggest benefits: (a) autonomous braking that would brake on its own, if the driver does not, to avoid a forward collision, and (b) adaptive headlights that would shift the headlights in the direction the driver steers. They found lane departure systems to be not helpful, and perhaps harmful, at the circa 2012 stage of development. A 2015 Insurance Institute for Highway Safety study found forward collision warning and automatic braking systems reduced rear collisions.[20]

A 2015 study based on European and Australasian data suggests the AEB can decrease rear-end collisions by 38%.[21]

In the 2016 Berlin terror attack, a truck was driven into the Berlin Christmas market and was brought to a stop by its automatic braking system.[22] Collision avoidance features are rapidly making their way into the new vehicle fleet. In a study of police-reported crashes, automatic emergency braking was found to reduce the incidence of rear-end crashes by 39 percent.[23] A 2012 study suggests that if all cars feature the system, it will reduce accidents by up to 27 percent and save up to 8,000 lives per year on European roads.[24][25]

In the UK and in the US, third party damages and costs have decreased by 10% and 40% according to some insurances.[10]

Features

Several features are commonly found across collision avoidance systems.

AEB systems shall detect possible collisions with the car in front.[26] It performs it with sensors to detect and classify things in front of the vehicle, a system to interpret the data from the sensors, and a braking system which can work autonomously.[27]

Pedestrian detection

Since 2004, Honda has developed a night vision system that highlights pedestrians in front of the vehicle by alerting the driver with an audible chime and visually displaying them via HUD. Honda's system only works in temperatures below 30 degrees Celsius (86 Fahrenheit). This system first appeared on the Honda Legend.[29]

ANCAP reports

The ANCAP report in its adult occupant protection section contains AEB rating taking into account AEB City from 10 to 50 km/h.

The ANCAP report in its vulnerable user protection section contains AEB rating taking into account both AEB and FCW for pedestrian and cyclists, with various speeds named "Operational from" (for instance 10 to 80 km/h) in the reports:

For pedestrians in day and night: adult crossing, child running, and adult walking along.

For cyclists in day only: cyclist crossing, cyclist traveling along.

The ANCAP report in its safety assist section contains AEB rating taking into account the AEB interurban with various speeds named "Operational from" (for instance 10 to 180 km/h):

reverse automatic braking

In the US, 5% of cars are able of reverse automatic braking. This feature allow in autonomous braking of the vehicle, while working in reverse direction, to avoid a reverse collision. Those systems are assesses by IIHS[31].

Automobile manufacturers

Various manufacturers provide AEB, but they might use different alternative names such as: [10]

City Safety – Volvo

SCBS – Smart City Brake Support – Mazda

Active City Stop – Ford

City Emergency Braking – Volkswagen

In countries, such as the UK, one quarter of new vehicles might have some kind of AEB system; but only 1% of previously sold cars might have AEB.[10]

Audi

2010: "Pre sense" autonomous emergency braking system uses twin radar and monocular camera sensors[32] and was introduced in 2010 on the 2011 Audi A8.[33] "Pre sense plus" works in four phases. The system first provides warning of an impending accident, activating hazard warning lights, closing windows and sunroof, and pretensioning front seat belts. The warning is followed by light braking to get the driver's attention. The third phase initiates autonomous partial braking at a rate of 3 m/s² (9.8 ft/s²). The fourth phase increases braking to 5 m/s² (16.4 ft/s²) followed by automatic full braking power, roughly half a second before projected impact. "Pre sense rear", is designed to reduce the consequences of rear-end collisions. The sunroof and windows are closed and seat belts are prepared for impact. The seats are moved forward to protect the car's occupants. 2015 introduced the "avoidance assistant" system that intervenes in the steering to help the driver avoid an obstacle. If an accident occurs, the "turning assistant" monitors opposing traffic when turning left at low speeds. In critical situation, it brakes the car. "Multicollision brake assist" uses controlled braking maneuvers during the accident to aid the driver. Both systems were introduced on the Second generation Q7.[34]

BMW

2012: BMW introduced two systems on the 7 Series. "Active Protection" detects imminent accidents to pretension safety belts, close windows and moonroof, bring backrest of the front passenger seat to an upright position, and activate post-crash braking. A driver drowsiness detection includes an advice to take a break from driving. An "Active Driving Assistant" combines lane departure warning, pedestrian protection, and city collision mitigation.

In 2013, "Driving Assistant Plus" was introduced on most models combining the front-facing camera, lane-departure warning, and in some cases front radar sensors to detect vehicles ahead. Should the driver not react to the warning of a potential collision, the system would gradually prime brake pressure and apply – with maximum deceleration power - if necessary. In the case of a crash, the system can bring the vehicle to a standstill. Later iterations of the system on cars equipped with Automatic Cruise Control system are improved by combining radar and camera detection during fog, rain, and other situations where normal camera operations may be compromised.

Ford

Beginning on the 2012 Ford Focus, Active City Stop was offered on the range topping Titanium model, under the optional Sports Executive Pack. The system used windscreen mounted cameras, radars, and lidars to monitor the road ahead. The system doesn't provide a warning, rather, it can prevent a crash occurring at speeds between 3.6 and 30 km/h (2.2 and 18.6 mph). This speed was later raised to 50 km/h (31 mph), and was available on all models, the Trend, Sport, Titanium, ST, and RS (Limited Edition only.)

General Motors

General Motors' collision alert system was introduced in GMC Terrain SUVs in 2012. It uses a camera to provide warning when there is a vehicle ahead or there is a lane departure.[35] The 2014 Chevrolet Impala received the radar- and camera-based crash imminent braking (radar technology detects a possible crash threat and alerts the driver. If the driver does not appear to react quickly enough or doesn’t react at all, this feature intervenes to apply the brakes in an effort to avoid the crash. Forward collision alert, lane departure warning, side blind zone alert (using radar sensors on both sides of the vehicle, the system “looks” for other vehicles in the blind zone areas of the Impala and indicates their presence with LED-lit symbols in the outside mirrors. Rear cross traffic alert features[36]

Honda

2003: Honda introduced an autonomous braking (Collision Mitigation Brake System CMBS, originally CMS) front collision avoidance system on the Inspire[37] and later in Acura, using a radar-based system to monitor the situation ahead and provide brake assistance if the driver reacts with insufficient force on the brake pedal after a warning in the instrument cluster and a tightening of the seat belts.[38][39] The Honda system was the first production system to provide automatic braking.[39] The 2003 Honda system also incorporated an "E-Pretensioner", which worked in conjunction with the CMBS system with electric motors on the seat belts. When activated, the CMBS has three warning stages. The first warning stage includes audible and visual warnings to brake. If ignored, the second stage would include the E-Pretensioner's tugging on the shoulder portion of the seat belt two to three times as an additional tactile warning to the driver to take action. The third stage, in which the CMBS predicts that a collision is unavoidable, includes full seat belt slack takeup by the E-Pretensioner for more effective seat belt protection and automatic application of the brakes to lessen the severity of the predicted crash. The E-Pretensioner would also work to reduce seat belt slack whenever the brakes are applied and the brake assist system is activated.[39]

Mercedes-Benz

2002: Mercedes' "Pre-Safe" system was exhibited at the Paris Motor Show on the 2003 S-Class. Using electronic stability control sensors to measure steering angle, vehicle yaw, and lateral acceleration and brake assist (BAS) sensors to detect emergency braking, the system can tighten the seat belts, adjust seat positions, including rear seats (if installed), raise folded rear headrests (if installed), and close the sunroof if it detects a possible collision (including rollover).[40] A later version of the Pre-Safe system was supplemented by an additional function that can close any open windows if necessary.

2006: Mercedes-Benz's "Brake Assist BAS Plus" was their first forward warning collision system introduced on the W221 S-Class, incorporates the autonomous cruise control system and adds a radar-based collision warning. 2006: the "Pre-Safe Brake" on the CL-Class C216[41] was their first to offer partial autonomous braking (40%, or up to 0.4g deceleration) if the driver does not react to the BAS Plus warnings and the system detects a severe danger of an accident.[42][43]

2009: Mercedes introduced the first Pre-Safe Brake with full (100%) autonomous braking with maximum braking force approximately 0.6 seconds before impact, on the Mercedes-Benz E-Class (W212).[44][45]

2013: Mercedes updated Pre-Safe on the W222 S-Class as plus with cross-traffic assist.[46] Pre-Safe with pedestrian detection and City Brake function is a combination of stereo camera and radar sensors to detect pedestrians in front of the vehicle. Visual and acoustic warnings are triggered when a hazard is spotted. If the driver then reacts by braking, the braking power will be boosted as the situation requires, up to a full brake application. Should the driver fail to react, Pre-Safe Brake triggers autonomous vehicle braking. Pedestrian detection is active up to about 72 km/h (45 mph) , and is able to reduce collisions with pedestrians autonomously from an initial speed of up to 50 km/h (31 mph).[46] A radar sensor in the rear bumper monitors the traffic behind the vehicle. If the risk of an impact from the rear is detected, the rear hazard warning lights are activated to alert the driver of the vehicle behind (not on vehicles with USA/Canada coding). Anticipatory occupant protection measures, such as the reversible belt tensioners, are deployed. If the vehicle is stopped and the driver indicates a wish to remain stationary – by depressing the brake pedal, activating the hold function, or moving the selector lever to "P" – the system increases the brake pressure to keep the vehicle firmly braked during a possible rear-end collision.[46] Pre-Safe Impulse works an early phase of the crash, before the resulting deceleration starts to increase, the front occupants are pulled away from the direction of impact and deeper into their seats by their seat belts. By the time the accident enters the phase when loads peak, the extra distance they are retracted by can be used while dissipating energy in a controlled fashion. Pre-acceleration and force limitation allow the occupants to be temporarily isolated from the effects of the crash, significantly reducing the risk and severity of injuries in a frontal collision.[46]

Nissan

Nissan's Infiniti brand offers both laser-based and radar-based systems. Brake assist with preview function anticipates the need to apply emergency braking and pre-pressurize the brake system to help improve brake response. Intelligent brake assist (IBA) with forward emergency braking (FEB) (on QX80) uses radar to monitor approaching speed to the vehicle ahead, helping detect an imminent collision. It provides a two-stage warning to alert the driver, and if the driver takes no action, the system automatically engages the brakes to mitigate the collision speed and impact. Predictive forward collision warning system warns the driver of risks that may be obscured from the driver's view. It senses the relative velocity and distance of a vehicle directly ahead, as well as a vehicle travelling in front of the preceding one. The forward emergency braking system judges that deceleration is required, it alerts the driver using both a screen display and sound, then generates a force that pushes the accelerator pedal up and applies partial braking to assist the driver in slowing the vehicle down. When the system judges that there is the possibility of a collision, it will automatically apply harder braking to help avoid one.

Subaru

Subaru's system, branded "EyeSight", was announced in May 2008 using stereo camera technology to detect pedestrians and bicyclists. As initially announced, EyeSight enabled pre-collision braking control and adaptive cruise control at all speeds.[47] It was rolled out in Japan to selected models in 2010; in Australia in 2011; and in North America in 2013 model year Legacy and Outback models.[48] An alarm is used to warn the driver of a potential collision hazard in the pre-collision system. The pre-collision braking control was upgraded in 2010 to allow the vehicle to stop automatically if the speed difference between the EyeSight-equipped vehicle and the object in front is less than 30 km/h (19 mph) and the driver takes no action to slow down or stop. Above 30 km/h (19 mph), the vehicle will reduce its speed automatically.[47] It also allows the vehicle to engage braking assist, if there is a risk of a frontal collision and the driver suddenly applies the brakes.[47] The speed difference to allow an automatic stop was raised to 50 km/h (31 mph) in 2013 with improved cameras.[49] The adaptive cruise control was also upgraded in 2010 to allow automatic emergency braking in traffic, fully stopping the EyeSight vehicle when the car in front has come to a complete stop.[47] In 2013, color was added to the cameras, allowing the system to recognize brake lights and red stoplights ahead.[49] Subaru also added an active lane-keeping (keeping the vehicle in the middle of the lane, and applying steering force to keep the vehicle in the lane when unintentionally crossing lane markers) and throttle management (to prevent sudden unintended acceleration in forward and reverse) systems in 2013 with the improved cameras.[49] EyeSight has been very popular, equipped on approximately 90% of all Legacy and Outbacks sold in Japan at the beginning of 2012,[48] and the engineers responsible for its development won a prize from the Japanese government that year.[50]

Toyota

Toyota's pre-collision system (PCS) is a radar-based system that uses a forward-facing millimeter-wave radar. When the system determines that a frontal collision is unavoidable, it preemptively tightens the seat belts, removing any slack, and pre-charges the brakes using brake assist to give the driver maximum stopping power when the driver depresses the brake pedal. 2003 February: Toyota launched PCS in on the redesigned Japanese domestic marketHarrier 2003 August: added an automatic partial pre-crash braking system to the Celsior.[51] 2003 September: PCS made available in North America on the Lexus LS 430, becoming the first radar-guided forward collision warning system offered in the US.

2004: In July 2004, the Crown Majesta radar PCS added a single digital camera to improve the accuracy of collision forecast and warning and control levels[52][53][54]

2006: Pre-collision system with Driver Monitoring System introduced in March 2006 on the Lexus GS 450h[52] using a CCD camera on the steering column. This system monitors the driver's face to determine where the driver is looking. If the driver's head turns away from the road and a frontal obstacle is detected, the system will alert the driver using a buzzer, and if necessary, pre-charge the brakes and tighten the safety belts. 2006: the Lexus LS introduced an advanced pre-collision system (APCS), added a twin-lens stereo camera located on the windshield and a more sensitive radar to detect smaller "soft" objects such as animals and pedestrians. A near-infrared projector located in the headlights allows the system to work at night. With the adaptive variable suspension (AVS) and electric power steering, the system can change the shock absorber firmness, steering gear ratios, and torque assist to aid the driver's evasive steering measures. The lane departure warning system will make automatic steering adjustments to help ensure that the vehicle maintains its lane in case the driver fails to react. Driver Monitoring System was introduced on the Lexus LS. Rear-end pre-collision system includes a rearward-facing millimeter-wave radar mounted in the rear bumper.[55] The system adjusts the active head restraints by moving them upward and forward to reduce the risk of whiplash injuries if an imminent rear collision is detected.[56]

2008: Improved Driver Monitoring System added on the Crown for detecting whether the driver's eyes are properly open.[57] It monitors the driver's eyes to detect the driver's level of wakefulness. This system is designed to work even if the driver is wearing sunglasses, and at night. 2008 PCS with GPS-navigation linked brake assist function on the Crown. The system is designed to determine if the driver is late in decelerating at an approaching stop sign, will then sound an alert and can also pre-charge the brakes to provide braking force if deemed necessary. This system works in certain Japanese cities and requires Japan specific road markings that are detected by a camera.

2009: Crown[58] added a front-side millimeter-wave radar to detect potential side collisions primarily at intersections or when another vehicle crosses the center line. The latest version tilts the rear seat upward, placing the passenger in a more ideal crash position if it detects a front or rear impact.[59]

2012: Higher Speed APCS on the Lexus LS enables deceleration from up to 37 mph (60 km/h), compared to the previous of 25 mph (40 km/h). The higher speed APCS uses the same technologies as then current APCS. This system increases the braking force up to twice that applied by average drivers. It was not then available in U.S. markets.

2013: Pre-collision system with pedestrian-avoidance steer assist and steering bypass assist[60] can help prevent collisions in cases where automatic braking alone is not sufficient, such as when the vehicle is travelling too fast or a pedestrian suddenly steps into the vehicle’s path. An on-board sensor detects pedestrians and issues a visual alert on the dashboard immediately in front of the driver if the system determines that there is a risk of collision. If the likelihood of a collision increases, the system issues an audio and visual alarm to encourage the driver to take evasive action, and the increased pre-collision braking force and automatic braking functions are activated.[61] If the system determines that a collision cannot be avoided by braking alone and there is sufficient room for avoidance, steer assist is activated to steer the vehicle away from the pedestrian.[62]

2016: Toyota announced it would make Toyota Safety Sense (TSS) and Lexus Safety System+ standard on nearly all Japan, Europe, and US models by the end of 2017.[63][64]

2017: Lexus introduced the updated Lexus Safety System+ 2.0 on the fifth generation LS. In the US 2017 model year, Toyota sold more vehicles equipped with collision warning than any other single brand with a total 1.4 million sold or 56% of their fleet.[65]

2018: Toyota released its updated Toyota Safety Sense 2.0 (TSS 2.0) to include Lane Tracing Assist, Road Sign Assist, and Low Light Pedestrian Detection with Daytime Bicyclist Detection which improves the Pre-Collision System. The first Japanese car model to receive (TSS 2.0) is the executive Crown in its 15th generation.

Volkswagen

Laser sensor of VW Up

2010: "Front Assist" on the 2011 Volkswagen Touareg can brake the car to a stop in case of an emergency and tension the seat belts as a precautionary measure.[66] 2012: Volkswagen Golf Mk7 introduced a "Proactive Occupant Protection" that will close the windows and retract the safety belts to remove excess slack if the potential for a forward crash is detected. Multi-collision brake system (automatic post-collision braking system) to automatically brake the car after an accident in order to avoid a second collision. City emergency braking automatically activates brakes at low speeds in urban situations. 2014: Volkswagen Passat (B8) introduces pedestrian recognition a part of the system. It uses a sensor fusion between a camera and the radar sensor. There is an "emergency assist" in case of a non-reacting driver, the car takes the control of the brakes and the steering until a complete stop.

Volvo

Volvo City Safety multiple camera

2006: Volvo's "Collision Warning with Auto Brake", developed in cooperation with Mobileye, was introduced on the 2007 S80. This system is powered by a radar/camera sensor fusion and provides a warning through a head up display that visually resembles brake lamps. If the driver does not react, the system pre-charges the brakes and increases the brake assist sensitivity to maximize driver braking performance. Later versions will automatically apply the brakes to minimize pedestrian impacts. In some models of Volvos, the automatic braking system can be manually turned off. The V40 also included the first pedestrian airbag, when it was introduced in 2012.

2013: Volvo introduced the first cyclist detection system. All Volvo automobiles now come standard with a lidar laser sensor that monitors the front of the roadway, and if a potential collision is detected, the safety belts will retract to reduce excess slack. Volvo now includes this safety device as an option in FH series trucks.[67]

2015: "IntelliSafe" with auto brake at intersection. The Volvo XC90 features automatic braking, if the driver turns in front of an oncoming car. This is a common scenario at busy city crossings as well as on highways, where the speed limits are higher.